Contrary to popular belief, Pit Bulls are not the most aggressive dogs. Statistically, small dogs, like Chihuahuas, Jack Russells, or Dauschunds are most likely to bite. Like any dog, it is entirely dependent on an individual dogs temperament and upbringing, and just like people, they are all different. There are no bad dogs, only bad owners.
While no individual breed is aggressive, the most reported bite incidents are from Rottweilers, Pitbull breeds, and German Shepherds. This is partially due to the fact that owners often use these breeds are popular, specifically as guard dogs, and that they have stronger bite pressure than other breeds.
No dog breed is any more likely to be aggressive than any other breed. Many dogs that have a reputation for aggression, such as pit bulls, German shepherds, and rottweilers, have this reputation because they are naturally bigger, stronger dogs and so when there is an incident with them they will usually cause more damage than another breed. These incidents also tend to be more publicized because of their breed, causing the reputation to get worse. A dog’s likelihood for aggression comes almost entirely from their background and temperament. Like people, dogs each have a different personality and some dogs tend to be more easily scared or stressed than others, which can lead to aggression if they are put in situations that make them extremely scared or stressed and are unable to get out of them. A dog’s background also can cause this; say, for instance, a dog was abused but is now living with a loving, responsible family that would never hurt it. Even though this family has never done anything to hurt the dog, something could trigger the dog into aggression, even something as small as a child trying to play with it. If something happens to the dog that was similar to something that happened in their abusive home, it can cause an aggressive reaction, which the dog sees as the most logical way to protect itself from harm. The vast majority of dog bites are caused by humans doing something accidentally that scares the dog, rather than the dog being naturally aggressive.
That being said, statistically speaking the majority of dog bites are caused by small breeds such as chihuahuas, Jack Russell terriers, Boston terriers, and dachshunds. This is little known because these bites are usually very minor, due to the dog’s small size. I personally believe, based on my experiences, that this is partially because of people’s tendency to carry, cuddle, and otherwise invade the personal spaces of these small dogs in the belief that they are cuddlier and cuter than big dogs, which can be incredibly scary and stressful for the dog. However, many small dogs do tend to have a more spirited and feisty temperament than big dogs, which may play a role in them being agitated to the point of biting more quickly.
Dog aggression really depends on how the dog is brought up and trained. If a dog is trained properly and given love, he or she will be less aggressive. In general, small dogs tend to be a little more aggressive and loud, they bark more and complain more. Larger dogs are usually less aggressive and loud because they have less to worry about due to their size. However, one of the most aggressive dogs are wolf-dog hybrids, because they are less domesticated.